Download Molecular Evolution

Chapter 01
Author: Lee Hannah
FIGURE 1.1 Earth ’ s Atmosphere. The atmosphere of the Earth is an amazingly thin layer
of gases. At its thickest, the atmosphere is approximately 100 km deep, which is less than
1/100th of the Earth ’ s diameter (12,700 km). Viewed in this perspective, the atmosphere
appears as a thin, vulnerable shroud around the Earth. Alterations to this gossamer
protective layer may have major consequences for life. Reproduced with permission from
NASA.
FIGURE 1.2 The Greenhouse Effect.
Solar radiation reaches the Earth, warming the surface. The surface then radiates longwave radiation back toward space. Greenhouse gases absorb and re-emit some of this
long-wave radiation. The net effect is that some radiation that would have escaped to space
is re-radiated within the atmosphere, causing warming. From Climate Change 2001: The
Scientifi c Basis . Intergovernmental Panel on Climate Change, 2001.
FIGURE 1.3 O cean Chemistry and Marine Life. Marine organisms such as these Pacifi c
white-sided dolphin ( Lagenorhynchus obliquidens ) are already experiencing ocean acidifi
cation. The pH of seawater varies signifi cantly by region and by depth, and it is increasing
due to human CO 2 emissions. CO 2 from human fossil fuel combustion enters
theatmosphere and then dissolves in seawater, making it more acidic. Surface waters already
contain about 30% more hydrogen ions than they did in pre-industrial times. Courtesy of
NOAA.